// 相当于就是取等号右边的结果了
enum FileAccess {
    // constant members
    None,
    Read    = 1 << 1,
    Write   = 1 << 2,
    ReadWrite  = Read | Write,
    // computed member
    G = "123".length
}
console.log(FileAccess.ReadWrite) // 6
console.log(FileAccess.None) // 0